Magnetron sputtering sources are used for treating, e.g. coating, a substrate, such as semiconductors, optical devices or flat panel displays. By such magnetron sources ions of a plasma are caused to sputter material from a target. This sputtered target material is then deposited on a surface of said substrate in order to form a thin film. Also, the ions may etch the substrate.
A sputter source having at least two electrically isolated stationary bar-shaped target arrangements mounted one alongside the other and separated by respective slits is already known (U.S. Pat. No. 6,093,293, see also U.S. Pat. No. 6,284,106 and U.S. Pat. No. 6,454,920). Each of the target arrangements includes a respective electric pad so that each target arrangement may be operated electrically independently from the other target arrangement. Each target arrangement also has a controlled magnet arrangement for generating a time-varying magnetron field upon the respective target arrangement. The sputter source further has an anode arrangement with anodes alongside and between the target arrangements and/or along smaller sides of the target arrangements.
Further, an arrangement for coating a substrate is known, which comprises two electrodes being electrically separated from a sputtering chamber and from each other, wherein one of the electrodes is a cathode being electrically connected with the target and wherein the other electrode is an anode (DE 40 42 289 A1). A capacitor and a resistor are connected in series to said anode and to ground. According to DE 41 36 655 A1 the capacitor can be omitted. In both documents (DE 40 42 289 A1 and DE 41 36 655 A1) the problem to be solved is to suppress an arc discharge.
If the anodes, as shown in DE 41 36 655 A1 are arranged in front of the cathode, the conditions of ignition are improved. However, the disadvantage occurs that the anodes are a hindrance for the current of plasma particles whereby the anodes are coated, too. This coating, in turn, leads to the result that particles of the anode can fall on the substrate and worsen the quality of the layer. On the other hand, with reactive sputtering, the surfaces of the anodes opposite to the surfaces of the cathodes may be coated with dielectric substances. As a result, the ignition conditions are worsened. This effect is known as the “disappearing anode”.
Still, a plasma source including a chamber for confining a feed gas is known (WO 2005/052979 A2). An anode is positioned in said chamber, and a segmented magnetron cathode comprising a plurality of magnetron cathode segments is positioned in the chamber proximate to the anode.
Finally, a plurality, i.e. more than two cathodes arranged in a chamber are known from U.S. Pat. No. 4,417,968, JP 2003-183829 and EP 1 594 153 A1.
It is an object of the present invention to provide an arrangement for coating a substrate, for instance glass, whereby the coating process has a long-term stability, so that the layers which are deposited on different substrates do not differ substantially from each other.